1. Technical Field
The present invention relates to acoustic transducers, and more particularly to an acoustic transducer whose vibrating membrane is centrally provided with a positioning member so as to define a vibratile portion that can vibrate freely, wherein the vibratile portion is peripherally provided with a plurality of elastic members that allow the vibratile portion to perform piston-like vertical vibration, thereby enhancing the sensitivity of the acoustic transducer.
2. Description of Related Art
MEMS microphones are known to have advantages of being compact and easy to manufacture, so are extensively used in mobile phones. A conventional acoustic transducer 80, as shown in FIG. 1, has a base plate 81, a back plate 82 and a vibrating membrane 83. The vibrating membrane 83 covers an opening 811 of the base plate 81, and the back plate 82 is deposited on the base plate 81 and separated from the vibrating membrane 83 by a gap 84. An electrode unit 85 is arranged on the back plate 82 and there is a fixing portion 821 that fixes an outer periphery of the vibrating membrane 83. Thereby, when the acoustic transducer 80 receives an acoustic wave, the vibrating membrane 83 vibrates and changes its distance from the electrode unit 85, causing change of capacitance.
When the acoustic transducer 80 receives acoustic waves and the vibrating membrane 83 deforms in the direction along which the acoustic waves advance, since the vibrating membrane 83 only has its periphery fixed to the base plate 81, the vibrating membrane 83 has its central part deforming more than its peripheral part, so the vibrating membrane 83 now forms an arc with its opening facing downward. This uneven deformation can cause the effective sensing area A of the vibrating membrane 83 significantly smaller than the working area of the vibrating membrane 83, leading to negative impact on the acoustic transducer 80 in terms of sensitivity and signal-to-noise ratio. Existing approaches to preventing the vibrating membrane from the arched deformation include increasing the thickness of the vibrating membrane and reducing the total area of the vibrating membrane in order to increase the vibrating membrane's rigidity. However, these existing approaches can be subject to increase manufacturing process complexity and manufacturing cost. Hence, there is a need for a feasible technical scheme for solving this problem.